PDF is a frozen page layout with no heading structure a machine can rely on. WebP is lossy or lossless depending on the encoder, with alpha and animation. ImageMagick sits between the two, and this page says exactly what happens to a PDF file on the way to becoming a WEBP one.
What runs when a PDF file becomes WEBP
ImageMagick 6.9.12, on a machine we rent and watch. Your PDF file is uploaded once, ImageMagick runs once, the WEBP comes back, and neither file is kept. PDF to WEBP is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the PDF into the WEBP
The pixel dimensions of your PDF file. The WEBP comes out the size the PDF went in, because nothing on this path resizes anything.
What PDF to WEBP costs you
Scalability. PDF describes shapes, WEBP stores a grid of pixels, and the engine rasterises at 150 dots per inch on the way across. That density is a deliberate choice: at the 72 dpi ImageMagick defaults to, an A4 PDF page comes out 595 pixels wide and reads as a failed conversion. Enlarge the WEBP afterwards and it blurs, because there is nothing left to redraw from.
The PDF text layer. A PDF usually carries selectable text; this path treats the page as a picture and paints it, so what comes out is an image of the page rather than its words.
If a model is going to read the WEBP
A WEBP file is pixels, and pixels are expensive for a model to read. Handed this WEBP, an assistant spends its budget looking at the picture rather than reading it, and it will paraphrase what it thinks it saw. If your PDF is mostly words, the useful move is to pull the text out of it, not to change which picture format holds it.
PDF to WEBP, measured rather than promised
Running PDF to WEBP against the real engine with a real file, ImageMagick wrote 906 bytes of WEBP in 0.1 seconds, machine otherwise idle. That is one PDF file on one day and not an average, which is why the number is given together with the file that produced it.
The PDF to WEBP verdict was reached by a format signature, meaning at least four bytes unique to the format were found at the right offset. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the WEBP file has anything inside it.
The same PDF file, sent somewhere else
Other outputs the probe measured out of a PDF file, so the cost of choosing WEBP can be read against something. Sizes do not compare across engines, because each family was probed with its own PDF witness file.
PDF to DOCX: 23,905 bytes in 0.9 seconds, verified by a format signature.
PDF to EPUB: 26,909 bytes in 0.9 seconds, verified by a format signature.
PDF to JPG: 5,782 bytes in 0.1 seconds, verified by a format signature.
PDF to PNG: 1,294 bytes in 0.1 seconds, verified by a format signature.
PDF to TXT: 219 bytes in 0.8 seconds, verified by reading the text back.
PDF to GIF: 9,463 bytes in 0.1 seconds, verified by a format signature.
Other ways into WEBP, and what they measured
Among the published routes into WEBP, PDF is the first largest output of the 8 measured. The witness files differ, so this ranks the probe run and not your document.
HEIC to WEBP: 416 bytes in under a tenth of a second.
HEIF to WEBP: 416 bytes in under a tenth of a second.
ICO to WEBP: 370 bytes in under a tenth of a second.
SVG to WEBP: 608 bytes in under a tenth of a second.
TIFF to WEBP: 370 bytes in under a tenth of a second.
What we will not pretend about PDF to WEBP
A PDF file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A PDF to WEBP run that passes 30 seconds is killed, and the ImageMagick process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
No text is read out of the PDF anywhere on this path. Converting a picture to WEBP never turns it into words, whatever the picture happens to contain.
ImageMagick was not saturated at sixteen simultaneous conversions: it held 47.5 a second while latency moved from 0.22 s to 0.34 s, and the service memory did not move off 51 MB. That is the measured headroom behind PDF to WEBP, not a marketing number.
One PDF file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
PDF to WEBP: what people ask
What actually converts my PDF file to WEBP?
ImageMagick does it, 6.9.12, on a machine we rent and watch. Not a browser trick and not somebody else service: the PDF file is uploaded once, ImageMagick runs once, the WEBP comes back, and neither file is kept afterwards.
How long does PDF to WEBP take?
On the file the probe used, ImageMagick took 0.1 seconds and wrote 906 bytes of WEBP. That is one real measurement on one real PDF file, not an average and not a promise about yours: a larger PDF takes longer, and past 30 seconds the run is stopped.
What do I lose going from PDF to WEBP?
The one to know about first: Scalability. PDF describes shapes, WEBP stores a grid of pixels, and the engine rasterises at 150 dots per inch on the way across. That density is a deliberate choice: at the 72 dpi ImageMagick defaults to, an A4 PDF page comes out 595 pixels wide and reads as a failed conversion. Enlarge the WEBP afterwards and it blurs, because there is nothing left to redraw from.
What pixel size does the WEBP come out at?
Whatever 150 dots per inch makes of your PDF, and that density is a decision rather than a default. A PDF carries shapes and page dimensions, never pixels, so a scale has to be fixed before a single pixel is drawn. If you need another size, the PDF is the file to go back to: of the two it is the only one that still knows the shapes.
Is PDF to WEBP free?
There is a free allowance every month, and one PDF to WEBP conversion costs half a credit against it. When the allowance runs out the tool says so and stops, rather than quietly handing you a worse WEBP.